1. Field of the Invention
The invention relates to any of a plurality of devices in a network which has the devices connected by short range communication in a dynamically changing network configuration. The present invention also relates to a program product applied for the devices.
2. Description of the Related Art
In recent years, various techniques using PAN (Personal Area Network) have been suggested. PAN is a network that includes devices such as cellphones, computers, and electrical appliances for home use and is capable of enabling short range communication among these devices on an ad-hoc basis by their wireless communication functions for example by Bluetooth technology. When a user having a cellphone capable of wireless communication for example by Bluetooth technology comes into the communication area of a PAN, the cellphone is added as a part of the PAN, and the network configuration of the plurality of devices dynamically changes.
One suggested service using a PAN is to allow image data stored in the memory of a cellphone to be transferred to another device having a display in the PAN, so that an image based on the image data is displayed on the display of the latter device.
In this service, the cellphone transmitting the image data discoveries for devices capable of carrying out the service among the plurality of devices in the PAN and displays IDs to specify the found devices in the form of a list on the display of the cellphone. Then, when the user of the cellphone selects one of the IDs in the list displayed on the display, the cellphone transfers the image data to the device corresponding, to the selected ID. In this way, the image is displayed at the device selected by the user.
Note that techniques related to such a network having devices such as a plurality of input/output devices and AV equipment and a computer connected with one another are disclosed for example by Japanese Patent Laid-Open Nos. 2000-244836, H09-154077, and 2002-305521.
In the conventional service as described above, when there are an enormous number of devices capable of carrying out the service, a list of IDs as many as the enormous number is displayed on the display. In this case, the user of the cellphone cannot effortlessly discern at a glance which is appropriately capable of carrying out the service among the enormous number of IDs and therefore inevitably spends much time for selecting a device.
The conventional service described above suffers from disadvantages related to difficulty in determination when a plurality of people try to use devices located close to one another at a time, processing when a plurality of users try to use the same device at the same time, and privacy protection for users when the content of a call changes. Furthermore, once a device moves and the network configuration of the group of devices capable of communication changes, a device selected based on a discovery result before the change might be no longer available for communication.